Name ___________________________________ Date ___________________ Period ____
Diffusion Virtual Lab
http://www.glencoe.com/sites/common_assets/science/virtual_labs/LS03/LS03.html
Background information:
A cell membrane permits some materials to pass through while keeping other materials out. Such a membrane is
called “selectively permeable.” Under normal conditions, water constantly passes in and out of this membrane.
This diffusion of water through a selectively permeable membrane is called osmosis. Like other substances, water
diffuses from an area of higher concentration to an area of lower concentration. When the movement of water
molecules in and out of a cell reaches the same rate, a state of equilibrium is reached.
If the concentration of water molecules is greater outside a cell, then the solution is hypotonic to the cell. Water
will move into the cell by osmosis. The pressure against the inside of the cell membrane will steadily increase. If
the pressure becomes great enough, the cell membrane will burst.
A solution is isotonic to the inside of the cell when there is the same concentration of water molecules on the
inside and outside of the cell membrane. To maintain equilibrium, water molecules move into and out of the cell at
the same rate.
Suppose a living cell is placed in a solution that has a higher salt concentration than the cell has. Such a solution is
hypertonic to the cell, because there are more salt ions and fewer water molecules per unit volume outside the cell
than inside. Water will move from the area of higher water concentration (inside the cell) to the area of lower water
concentration (outside the cell). The selectively permeable membrane does not allow salt ions to pass into the cell.
The cell shrinks as the cell loses water.
Objectives:
• Describe the process of osmosis
• Observe the movement of water through cell membranes during the process of osmosis
• Compare and contrast three osmotic states: hypotonic, isotonic, and hypertonic
Procedure:
Red Blood Cell
__1. Select the red blood cell at the top of the screen and drag it into the hypotonic beaker.
__2. Observe the process of osmosis. Determine whether water (represented as blue arrows) moves into, stays
in equilibrium, or moves out of the cell. Observe what happens to the shape and size of the cell.
__3. Record your observations in the Data Table.
__4. Click at the bottom. Now drag the red blood cell to the isotonic beaker. Observe the process of
osmosis again and record your observations in the Data Table.
__5. Click at the bottom. Now drag the red blood cell to the hypertonic beaker. Observe the process
of osmosis again and record your observations in the Data Table.
Elodea Cell
__1. Select the elodea cell at the top of the screen and drag it into the hypotonic beaker.
__2. Observe the process of osmosis. Determine whether water (represented as blue arrows) moves into, stays
in equilibrium, or moves out of the cell. Observe what happens to the shape and size of the cell.
__3. Record your observations in the Data Table.
__4. Click at the bottom. Now drag the elodea cell to the isotonic beaker. Observe the process of
osmosis again and record your observations in the Data Table.
__5. Click at the bottom. Now drag the elodea cell to the hypertonic beaker. Observe the process of
osmosis again and record your observations in the Data Table.
Paramecium Cell
__1. Select the paramecium cell at the top of the screen and drag it into the hypotonic beaker.
__2. Observe the process of osmosis. Determine whether water (represented as blue arrows) moves into, stays
in equilibrium, or moves out of the cell. Observe what happens to the shape and size of the cell.
__3. Record your observations in the Data Table.
__4. Click at the bottom. Now drag the paramecium cell to the isotonic beaker. Observe the process
of osmosis again and record your observations in the Data Table.
__5. Click at the bottom. Now drag the paramecium cell to the hypertonic beaker. Observe the
process of osmosis again and record your observations in the Data Table.
